CN104202260A - Scheduling method of backpressure link based on geographic position - Google Patents

Abstract

The invention discloses a scheduling method of a backpressure link based on a geographic position. The scheduling method comprises the following steps of: dividing a data packet in each node into different queues according to difference of transmission of target nodes, and storing; determining an optimal target node based on the length of the queues and a distance vector; carrying out scheduling of the link, and determining a network data transmission matrix through a weighting network throughput maximization principle under the condition of a feasible network transmission rate matrix; and carrying out rate distribution on the link, that is to say, if one link is selected to transmit, utilizing all bandwidths of the link to transmit and taking the transmission rate as a maximum value of the data transmission rate of the link. According to the scheduling method, a forwarding path can be stably and efficiently determined in a dynamically-changeable communication network environment, so that the purpose of end-to-end delay in the network is implemented.

Description

A kind of back pressure link scheduling method based on geographical position

Technical field

The present invention relates to scheduling and the route technology field of communication network, particularly a kind of back pressure link scheduling method based on geographical position.

Background technology

In queuing network, back pressure algorithm can ensure under the prerequisite of network stabilization, network throughput to be maximized, and solution overall network Parameter Conditions that can be strong situation about constantly changing in time.

Due to the shortage of spectral bandwidth resource in recent years, back pressure algorithm has obtained paying close attention to widely.Based on dynamic resource distribution and Path selection, back pressure algorithm can be realized the transmission in multihop network by congested gradient.

But traditional back pressure algorithm probably causes larger end-to-end delay, what especially when offered load is smaller, this drawback embodied is more obvious.Because at offered load hour,, back pressure algorithm need to be searched for the stability that a lot of unnecessary paths keep network.Consider a kind of extreme condition environment: only have a packet to enter this network.Owing to there is no the sensing destination node barometric gradient of moulding, this packet selecting paths is randomly strolled in network, and does not very likely forever all arrive destination node.Another shortcoming of this algorithm is: the feature that back pressure algorithm is ignored destination node information has completely caused Path selection to have certain blindness, may cause route loop or select unnecessary long path etc.

Thereby in the research process of follow-up back pressure algorithm, how on the basis that ensures maximum throughput and network stabilization, to be all the emphasis of research all the time.

At present about the research of back pressure algorithm have following some: the first, reduce time delay with lifo queue management algorithm replacement fifo queue management algorithm; The second, not affecting under the condition of network capacity, shortest path is converted into the routine weight value in back pressure algorithm, thereby reaches the target that reduces end-to-end delay; The 3rd, to each transmitting data stream compute best paths length, reduce average end-to-end delay with this, and in back pressure algorithm, carry out the transmission of data dispatching bag by this value as the path upper limit.

The reasonability of these methods is proved to be, and can ensure, under the throughput-maximized and sufficiently stable condition of overall network, to reduce the average delay of radio network end-to-end.But the method for queue management is not utilized the information of destination node, also there is the problem of route loop; Need in network, exchange messages to the calculating in path, bring overhead.

Summary of the invention

The shortcoming that the object of the invention is to overcome prior art, with not enough, provides a kind of back pressure link scheduling method based on geographical position.

Object of the present invention realizes by following technical scheme:

A back pressure link scheduling method based on geographical position, the step that comprises following order:

S1. set up queuing model: detect the state of each node and individual link, each node of network is classified as the packet of different destination nodes in different buffer queues, and calculate the packet cumulative amount of each queue, overstock;

S2. select the optimum destination node of every link: the buffer memory that arrives the distance vector weighting of destination node by node overstocks, obtain and make link weight overstock poor maximum destination node, this destination node is optimum destination node; Described node, to the distance vector of destination node, first obtains the positional information of node and destination node by existing navigation system, then calculate;

S3. link scheduling: the maximized principle based on weighted network throughput is calculated optimal network transmission rate matrix;

S4. the selection of link transmission speed: for given speed rates rate matrix, transmit optimum destination node packet on fixed link time, the transmission rate value of the maximum possible that the value of its transmission rate is this link.

In step S2, described link weight overstocks poor definite by following formula:

$Q_{\mathrm{ab}}\left(t\right)=\underset{\{c\≠a\}}{\max }\{U_a^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}-(D_b^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}/D_a^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)})U_b^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}\}$

$c_{\mathrm{ab}}^{\mathrm{opt}}=\arg \underset{\{c\≠a\}}{\max }\{U_a^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}-(D_b^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}/D_a^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)})U_b^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}\}$

Wherein, Q _ab(t) be the weighted product pressure reduction of link ab;

for optimum destination node corresponding to link ab;

the destination node storing in buffering area for node a is and the amount of the packet not sending;

for node b is to destination node geographic distance;

for node a is to destination node geographic distance;

the destination node storing in buffering area for node a is and the amount of the packet not sending.

Described step S3, specifically comprises following steps:

Optimal matrix is defined as ${\mathrm{\μ}}^{\mathrm{opt}}\left(t\right)=\left({\mathrm{\μ}}_{\mathrm{ab}}^{\mathrm{opt}}\left(t\right)\right);$

At the feasible link rate matrix of network (μ _ab(t)) ∈ Γ _{s (t)}situation under, make weighted network throughput: obtain maximum matrix (μ _ab(t)) be optimal rate matrix μ ^opt(t);

Wherein, Q _ab(t) be the weighted product pressure reduction of link ab; μ _ab(t) be the transmission rate on link ab, (μ _ab(t)) the serve as reasons network link rate matrix of each link transmission speed composition, μ ^opt(t) be the optimum rate matrix after as calculated, for the optimal rate matrix of link ab.

The described back pressure link scheduling method based on geographical position, the transfer of data of communication network is operated in different time-gap, and the data transmission procedure that step S1-S4 describes is operated in a time slot, and communication network is pressed the continuous repeating step S1-S4 of slot cycle.

Compared with prior art, tool has the following advantages and beneficial effect in the present invention:

1, the present invention is in conjunction with the navigation system of practical application, the definition that positional distance variable is overstocked with node in traditional back pressure algorithm combines, and redefined overstocked poor on link.

2, the present invention introduces the information of positional distance, thereby using positional distance gradient has solved traditional back pressure algorithm and has caused the even problem of circulating path of larger transmission delay at offered load compared with hour cannot being correctly sent to destination node owing to there is no enough congested gradients, also avoid system due to the unknown of destination node position is caused to back pressure algorithm search, sought unnecessary long path.

3, the network of introducing the inventive method can be guaranteed the stability of network.

Be embodied in and use range information weighting buffer memory to overstock, make data retransmission produce larger back pressure in destination node direction, shorten transmission path, reduce transmission delay.

Brief description of the drawings

Fig. 1 is the flow chart of the dispatching method of the back pressure algorithm based on geographical position of the present invention;

Fig. 2 is node and link schematic diagram in method described in Fig. 1.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited to this.

As Fig. 1, a kind of back pressure link scheduling method based on geographical position, the step that comprises following order:

S1. wait for that packet arrives node, until node cushions the non-vanishing next step that just carries out;

S2. set up queuing model: in time slot t, detect the state of each node and individual link, each node of network is classified as the packet of different destination nodes in different buffer queues, and calculate the packet cumulative amount of each queue, overstock;

S3. select the optimum destination node of every link: the buffer memory that arrives the distance vector weighting of destination node by node overstocks, obtain and make link weight overstock poor maximum destination node, this destination node is optimum destination node; Described node, to the distance vector of destination node, first obtains the positional information of node and destination node by existing navigation system, then calculate;

Described link weight overstocks poor definite by following formula:

$Q_{\mathrm{ab}}\left(t\right)=\underset{\{c\≠a\}}{\max }\{U_a^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}-(D_b^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}/D_a^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)})U_b^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}\}$

$c_{\mathrm{ab}}^{\mathrm{opt}}=\arg \underset{\{c\≠a\}}{\max }\{U_a^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}-(D_b^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}/D_a^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)})U_b^{\left(c_{\mathrm{ab}}^{\mathrm{opt}}\right)}\}$

Wherein, Q _ab(t) be the weighted product pressure reduction of link ab;

for optimum destination node corresponding to link ab;

the destination node storing in buffering area for node a is and the amount of the packet not sending;

for node b is to destination node geographic distance;

for node a is to destination node geographic distance;

the destination node storing in buffering area for node a is and the amount of the packet not sending;

S4. link scheduling: the maximized principle based on weighted network throughput is calculated optimal network transmission rate matrix; Specifically comprise following steps:

Optimal matrix is defined as ${\mathrm{\μ}}^{\mathrm{opt}}\left(t\right)=\left({\mathrm{\μ}}_{\mathrm{ab}}^{\mathrm{opt}}\left(t\right)\right);$

At the feasible link rate matrix of network (μ _ab(t)) ∈ Γ _{s (t)}situation under, make weighted network throughput: obtain maximum matrix (μ _ab(t)) be optimal rate matrix μ ^opt(t);

Wherein, Q _ab(t) be the weighted product pressure reduction of link ab; μ _ab(t) be the transmission rate on link ab, (μ _ab(t)) the serve as reasons network link rate matrix of each link transmission speed composition, μ ^opt(t) be the optimum rate matrix after as calculated, for the optimal rate matrix of link ab;

S5. the selection of link transmission speed: for given speed rates rate matrix, transmit optimum destination node packet on fixed link time, the transmission rate value of the maximum possible that the value of its transmission rate is this link.

S6. the transfer of data of communication network is operated in different time-gap, and the data transmission procedure that step S2-S5 describes is operated in a time slot t, and communication network is pressed the continuous repeating step S2-S5 of slot cycle.

Illustrate with a concrete example below:

A dispatching method for back pressure algorithm based on geographical position, comprises following steps:

As Fig. 2, wireless network comprises 4 nodes, and 4 nodes are alternately connected: 1-2-3-4-1 forms an annular and connects, and queue in each node is: node 1:{1,4}=6, { 1,3}=6; Node 2:{2,4}=2, { 2,3}=2; Node 3:{3,4}=3, { 3,3}=0; Node 4:{4,4}=0, { 4,3}=2.

(1) set up queue: detect each node and each Link State, by the difference of destination node, the packet in this node is divided into different queue and stores;

(2) select optimum destination node: analyze link (1,2): $U_2^{\left(4\right)}\left(t\right)=U_2^{\left(3\right)}\left(t\right)=2;$ And then try to achieve link overstock poor: $Q_{12}^{\left(3\right)}\left(t\right)=5,Q_{12}^{\left(4\right)}\left(t\right)=2;$ The former is larger, so backward the overstocking of this link is 5, its corresponding best destination node is node 3;

(3) select optimal transmission rate matrix: from actual transfer rate space, select best link transmission rate matrix according to the principle that makes weighted network throughput maximum.

(4) according to the optimum destination node drawing in (2), from (3) matrix, select corresponding transmission rate, and regulation is for the selected transmission link peak transfer rate that its transmission rate is this link; For in this example: its transmission rate of link (1,2) is element μ in matrix ₁₂, and the transmission rate of link (Isosorbide-5-Nitrae) is 0 (t);

(5) according to (1)-(4) step, all nodes in network are implemented to as above operation; Until the whole end of transmissions of packet.

Above-described embodiment is preferably execution mode of the present invention; but embodiments of the present invention are not restricted to the described embodiments; other any do not deviate from change, the modification done under Spirit Essence of the present invention and principle, substitutes, combination, simplify; all should be equivalent substitute mode, within being included in protection scope of the present invention.

Claims (4)

1. the back pressure link scheduling method based on geographical position, is characterized in that the step that comprises following order:

S1. set up queuing model: detect the state of each node and individual link, each node of network is classified as the packet of different destination nodes in different buffer queues, and calculate the packet cumulative amount of each queue, overstock;

S2. select the optimum destination node of every link: the buffer memory that arrives the distance vector weighting of destination node by node overstocks, obtain and make link weight overstock poor maximum destination node, this destination node is optimum destination node; Described node, to the distance vector of destination node, first obtains the positional information of node and destination node by existing navigation system, then calculate;

S3. link scheduling: the maximized principle based on weighted network throughput is calculated optimal network transmission rate matrix;

S4. the selection of link transmission speed: for given speed rates rate matrix, transmit optimum destination node packet on fixed link time, the transmission rate value of the maximum possible that the value of its transmission rate is this link.

2. the back pressure link scheduling method based on geographical position according to claim 1, is characterized in that, in step S2, described link weight overstocks poor definite by following formula:

Wherein, Q _ab(t) be the weighted product pressure reduction of link ab;

for optimum destination node corresponding to link ab;

the destination node storing in buffering area for node a is and the amount of the packet not sending;

for node b is to destination node geographic distance;

for node a is to destination node geographic distance;

the destination node storing in buffering area for node a is and the amount of the packet not sending.

3. the back pressure link scheduling method based on geographical position according to claim 1, is characterized in that described step S3 specifically comprises following steps:

Optimal matrix is defined as

At the feasible link rate matrix of network (μ _ab(t)) ∈ Γ _{s (t)}situation under, make weighted network throughput: obtain maximum matrix (μ _ab(t)) be optimal rate matrix μ ^opt(t);

Wherein, Q _ab(t) be the weighted product pressure reduction of link ab; μ _ab(t) be the transmission rate on link ab, (μ _ab(t)) the serve as reasons network link rate matrix of each link transmission speed composition, μ ^opt(t) be the optimum rate matrix after as calculated, for the optimal rate matrix of link ab.

4. the back pressure link scheduling method based on geographical position according to claim 1, it is characterized in that: the described back pressure link scheduling method based on geographical position, the transfer of data of communication network is operated in different time-gap, the data transmission procedure that step S1-S4 describes is operated in a time slot, and communication network is pressed the continuous repeating step S1-S4 of slot cycle.